This invention relates to a packaging machine of the so-called form-fill-seal type adapted to concurrently form a bag from a film, to fill it with articles and to seal it to obtain individual packaged products. More particularly, this invention relates to a method of and a device for adjusting the position on the film at which it is cut ("cut-position") to produce separated bags. The invention also relates to a packaging machine adapted to automatically adjust the cutposition according to an inputted size of the bags to be produced.
Packaging machines adapted to concurrently bend a film into a tubular form, to fill it with articles to be packaged and to clamp it between a pair of sealing members ("seal jaws") to simultaneously seal the top part of a filled bag and the bottom of the next bag to be filled have been known. If the bags are formed from a film with a design printed thereon corresponding to each bag to be formed, marks (hereinafter referred to as the "eye marks") which are detectable by a light sensor are printed on the film at longitudinal intervals corresponding to the length of the bags to be made such that the film can be accurately sealed over and cut at boundary areas between portions of the film corresponding to two mutually adjacent bags as the packaging machine is operated to repeat a cyclic motion.
Prior art methods of determining the cut-position of the bags or the clamping position by seal jaws can be roughly divided into those of adjusting the interval between the time when an eye mark on the film as a reference is detected and the time at which the film is cut (such as adjusting the dislocation of the cut-position while changing the time set on a timer by operating a dial) and those of displacing the position of the sensor for the eye marks (that is, to move the eye mark sensor by a distance corresponding to the displacement of the cut-position). The methods of the former kind are not desirable because repeated trials and errors tend to increase the wasted amount of the film. The methods of the latter kind are advantageous in that one has only to displace the eye mark sensor but it is a cumbersome operation to make the position adjustment while watching the markings of a dial.
In the case of packaging machines of a continuously operated type having a linearly moving transverse sealing mechanism, in particular, the cut-position of the film also changes whenever the stripping distance is changed according to the kind of the articles to be packaged or the pattern of motion (such as the time of sealing) for the transverse seal jaws. Thus, the operator had to adjust the cut-position whenever such a change had to be made. This also contributed to increase the waste of the film material.